This invention relates generally to packaging systems, and more particularly to methods for making flexible packages of the kind shown in my copending earlier application having an openable and reclosable interlocking seal which may be further provided with a center hinge and lateral side snap detents spaced along the length of the seal, the reclosable interlocking seal having male and female parts with the detents being formed in the female part and extending into the male part. The seal structure provides tactile and auditory snap indications of the state of the seal during opening and closing of the package. The methods for making such packages utilize a continuous web of composite film moving at line speed.
In the past, the methods of making reclosable flexible packages have usually involved either the extrusion of a two part zipper type locking structure along with the film extending longitudinally in the direction of film extrusion along the opposite edges of the film, or by heat sealing a separately made extruded zipper type locking structure to the package film. The first type of package formation results in packages having the reclosable feature in the consumer non-preferred position along the long edge of the package, while the second type of package formation results in packages which are expensive to make because of the need to inventory and store rolls of the separate zipper structure for attachment to the packaging film and the need to insure that the separately obtained packaging film and zipper are made of compatible materials. Consumer focus groups have disclosed dissatisfaction with both types of zipper structure for various reasons, such as user frustration because of difficulty in reclosing the zippers, and no feedback to the user that the zipper has in fact been engaged.
Shown and described in my earlier application is a resealable interlocking closure of the same general kind as shown and described in this application, but which does not utilize the film and strip technology of the present invention, and does not include the improved features of the present invention.
The package and system according to the present invention utilize a novel composite packaging film structure comprising the packaging film with strips of formable plastic laminated to the film at package length intervals. The composite packaging film structure may be preformed and stored as roll stock material or may be concurrently made by a Sig Pack, Inc. Easy Snap(trademark) Laminator mounted atop or adjacent to the packaging apparatus to form the novel composite packaging film structure, which composite film is then fed into the packaging apparatus to form the finished package incorporating the novel reclosable seal formed in the film and strip composite. The laminator functions with both horizontal and vertical form/fill/seal wrapping machines and with overwrap packagers, and laminates various plastic strip materials to diverse heat seal packaging films.
The packaging films could be for example, polypropylene, polyethylene, polystyrene, polyvinylchloride, thermoplastic heat seal coated non-plastic films, and various film laminations of two to four layers, while the plastic strip could be formed of one to three layers. In some applications the strip could be a single thickness of polyvinylchloride (PVC) heat sealed to a PVC film at a temperature of about 230xc2x0 F. for xc2xd to xc2xe seconds, while in other applications the strip could be of two layers such as PVC plus a sealing layer, or three layers such as a center layer coated on opposite sides respectively with a sealing layer and a release layer to prevent the strip from self adhering during formation of the reclosable interlock seal. A commonly used packaging film is a four layer film consisting of two layers of polypropylene separated by a layer of low density polyethylene and having a heat seal layer of low density polyethylene coated on one face.
The invention is shown and described in conjunction with a modified vertical form, fill and seal packaging machine having a novel fill tube forming collar and novel package sealing press which latter also forms the novel resealable closure, the packaging machine being for example a Sig Pack, Inc. Eagle Infinity, Model 1524.
Packages made according to the invention incorporating the novel reclosable seal address the consumer complaints relating to prior art zipper seals by providing clear auditory and tactile indications of the closing of the reclosable seal by incorporation of snap detents, so that the consumer is assured that the package has been resealed even in the absence of visual package inspection.
Accordingly, it is a primary object of the invention to provide novel methods of making openable and reclosable interlocking seals for packages.
Another object of the invention is to provide novel methods of making packages having openable and reclosable interlocking seals.
An additional object of the invention is to provide novel methods of making a package having an openable and reclosable interlocking seal as aforesaid in which the bulk of the seal structure is provided by an added layer of strip material secured in a specific way to the packaging film at package length intervals.
A yet further object of the invention is to provide novel methods of making a package having an openable and reclosable interlocking seal as aforesaid in which the ends of the strip material are positioned in abutment at substantially the center of one face of the package to provide a hinge to assist in package opening.
Still another object of the invention is to provide novel methods of making a reclosable interlocking package seal having male and female parts with snap detents being formed in the parts, the closure structure providing tactile and auditory snap indications of the state of the closure during opening and closing of the package.
A yet further object of the invention is to provide novel methods of making packages as aforesaid in which the reclosable interlocking seal is formed from the packaging film and a heat sealable strip heat sealed to the packaging film.
A still further object of the invention is to provide novel methods of making packages as aforesaid in which the packages may be formed from a variety of packaging films such as polypropylene, polyethelene, polystyrene, polyvinylchloride, and various film laminates.